: Question for Gearing and Math Gurus



thebigjimsho
08-19-06, 09:33 AM
So, depending on what magazine you go by and personal experience, the V's top speed is between 161-165mph. If my grand plans come to fruition, I figure to have some head and cam work done and plan on raising the rev limiter.

So...if on stock tires, what should the top speed be in the V at 7000rpm in 5th gear? Also, what would it be at 7,200rpm in 5th gear?

I'm also assuming that I still won't have enough hp to accelerate in 6th, so we'll leave that alone. But I'm betting some will still comment about this...

The Tony Show
08-19-06, 09:40 AM
Unless you raise the top speed limiter, it'll still be 163 mph. Both 5th and 6th are capable of reaching this speed without taching out- it's the top speed limiter that keeps you from going higher, not the rev limiter.

NOW GIVE ME REP POINTS!

(sorry. :D)

wildwhl
08-19-06, 09:59 AM
I could be wrong here, but I understood the V didn't have an electronic limiter, but was drag limited to (insert max mph here)?

I know I've never seen anyhing over 145 mph on my speedo :nono: Don't have the guts on these limited roads in my part of the world.

WW

CIWS
08-19-06, 10:08 AM
My speed limiter is set at 168mph and I haven't altered it.

http://www.ciws.net/ctsv/speedlimiter.jpg

wildwhl
08-19-06, 10:09 AM
Duh, I guess I could have fired up the other laptop and looked.

Bigjim - I don't know the answer to your question. I do remember StealthV posting a chart for shift points that reflected MPH/RPM in each gear or something? Searched and can't find it.

WW

CIWS
08-19-06, 10:12 AM
You could do some rough SWAG by watching the video up on the FAQ site of the 160mph run and try to see how much rpms are increasing vs mph in 5th gear and get a rough idea of what the difference might be.

The Tony Show
08-19-06, 10:13 AM
Speed @ redline (Except 5th and 6th)

1st- 46mph
2nd- 66mph
3rd- 96mph
4th- 137mph
5th- 163mph
6th- 163 mph

Those are the official GM specs. Tire size, inflation and road condition can net you slightly higher or lower results.

The Tony Show
08-19-06, 10:15 AM
Just for hee-haws, here's the gear ratios:

1st- 2.97:1
2nd- 2.07:1
3rd- 1.43:1
4th- 1.00:1
5th- 0.84:1
6th- 0.56:1
Final Drive- 3.73:1

Reverse- 3.28:1

thebigjimsho
08-19-06, 10:40 AM
MAN! I saw 7 replies and thought I was missing out in Gearing 101!!

Tony, if I'm doing all this head and cam work, not to mention headers and exhaust and intake, I will be getting it tuned as well. So bye bye to the stock settings.

Hence, the reason for the question.


BTW, wild, got the wheels on Thursday. Thank you!!!!!!!!!!!!!!!!!!!!!!!!!!!!

thebigjimsho
08-19-06, 10:54 AM
OK, I do need to give thanks to Mr. Orlando for giving us those numbers with regards to gear ratio and speed.

I did some math and confirmed that each ratio posted and corresponding speed posted were accurate. So...

Pretty simple math from there. IF 163mph were achieved at 6500rpm, then you divide as such 7000rpm/6500rpm = 1.076923. Multiply that by 163mph and you get 175.538mph. Now, if you bump this up to 7200rpm/6500rpm = 1.1076923. Multiply that by 163mph and you get 180.554mph.

So, IF you don't reach the drag limited top speed, you SHOULD be able to hit 175mph @ 7000rpm and 180mph @ 7200 rpm.

Good stuff.

If I'm wrong, please let me know! and don't forget rep points for doing math on a saturday morning...

The Tony Show
08-19-06, 11:04 AM
"Mister Orlando".... I like the sound of that.

If you plan on revving that high in the lower gears Jim, make sure you get stiffer valve springs to go with that cam. I'm jealous of the mods you're doing- have fun!

2004ctsv
08-19-06, 11:06 AM
Jimbo

Check some of the really old threads - 2004 time frame

The concensus was that with stock configuration, you'll never see 163 in 6th - too much drag at speed/rpm well below peak hp

There's only one sure way to find out and it ain't on a dyno

T

The Tony Show
08-19-06, 11:22 AM
I would agree. Since top speed is reachable in 5th, you would never bring 6th into play for any reason other than gas mileage while cruising (or if you're cruising at 150, to keep from cooking the cats).

JonCR96Z
08-19-06, 11:41 AM
Using the calculator at http://www.f-body.org/gears/

Its showing 177 @ 7000 and 182 @ 7200, but it also show 165 at 6500. So it looks like you're pretty close BigJim.

I'm assuming difference maybe that the calculated tire size may not be accurate. Since it is just a basic math formula (245mm/45 * 2 + 18inches). Afterall I've seen different brands of the same size be half an inch difference(not nessecarily talking about V tires).

Jon

StealthV
08-19-06, 11:47 AM
5th gear @ 7000 rpm = ~171 mph
5th gear @ 7200 rpm = ~176 mph

thebigjimsho
08-19-06, 12:16 PM
"Mister Orlando".... I like the sound of that.

If you plan on revving that high in the lower gears Jim, make sure you get stiffer valve springs to go with that cam. I'm jealous of the mods you're doing- have fun!
Si, senor Orlando! If I only do cam, the stock redline would be used...maybe a couple more hundred rpm couldn't hurt...

But if I want to really make the V a track machine, new springs is in the cards with regards to heads.

50 4Ever
08-21-06, 06:42 PM
Before anyone does anything stupid remember that the stock F1's and the stock size Gs-D3's have a speed rating of W, which is 168 MPH. It would not be wise to go 180 MPH on a tire that could fly apart. If you want to go faster look for some tires that have a speed rating of Y, which is 186 MPH.

I have never had the V over 120 MPH, but I know for a fact that my '03 Corvette is drag limited in 6th at about 147 MPH. Shifting down to 5th is the only way to attain top speed, again I'm a chicken - only had it up to 160MPH for 10 minutes, then I slowed back down and cruised at 124 MPH for about 30 minutes, until I got close to Beatty Nevada.

:thumbsup:

StealthV
08-21-06, 07:48 PM
Speed rating? Bah - Didn't anyone else besides me do 150+ mph twenty years ago in old muscle cars with crappy bias ply tires, drum brakes and mushy handling? :)

wildwhl
08-21-06, 08:38 PM
Beatty Nevada? Watch out there...seriously. Should only be >150 for about 7 minutes :sneaky:

WW

Luna.
08-21-06, 10:41 PM
If you plan on revving that high in the lower gears Jim, make sure you get stiffer valve springs to go with that cam.

:yeah:

"Mr Orlando" beat me to it. :)

And I seriously doubt that anyone would run into any significant problems briefly hitting ~180mph with a W rated tire. Now, if you were going to go out and maintain that speed for any significant length of time...

Dennisscars
08-22-06, 12:26 AM
Speed rating? Bah - Didn't anyone else besides me do 150+ mph twenty years ago in old muscle cars with crappy bias ply tires, drum brakes and mushy handling? :)
:hmm: hmm.. didn't know you were a moonshiner... but them were the days.. you knew you were passin' some earth under your arse.. (mostly 'cause you could see it through the floor board..)

thebigjimsho
08-22-06, 09:19 AM
:yeah:

"Mr Orlando" beat me to it. :)

And I seriously doubt that anyone would run into any significant problems briefly hitting ~180mph with a W rated tire. Now, if you were going to go out and maintain that speed for any significant length of time...Yeah, I would love to get to Buffalo from Boston in just over 2 hours.:bouncy:

SlvrVee
08-22-06, 11:52 PM
WW this what you were thinking about Stealth had posted it a while back


For your car, the shift points for maximum acceleration force are:

1 > 2 = 6650
2 > 3 = 6900
3 > 4 = 6850
4 > 5 = 6300
5 > 6 = 7200

v-ape
08-23-06, 10:21 AM
So, IF you don't reach the drag limited top speed, you SHOULD be able to hit 175mph @ 7000rpm and 180mph @ 7200 rpm.

Good stuff.

If I'm wrong, please let me know! and don't forget rep points for doing math on a saturday morning...



CTS-V Drag:

D=Cd*1/2*density*(Velocity^2)*(Frontal Area)

Cd=0.354
Frontal Area = 23.7 ft^2

Assuming standard day... (density = 0.00237 slug/ft^3)

Drag:
65mph = 90lbs
163mph = 568lbs.
175mph = 654lbs.